U-Value Calculator
Calculate U-values for walls, roofs and floors using Recticel Insulation's free online U-value calculator. Find out about how this calculation is done exactly and which steps you go through.
Calculator What is a U-Value CalculationFAQs
Calculations derived from the online U-value calculator are designed to be indicative only and Recticel Insulation accepts no liability for errors in calculations. Any specification should be approved by the design and management authority to ensure it meets project specific and regulatory requirements. Recticel Insulation cannot be held responsible for design errors. For a more formal and accurate calculation and condensation risk analysis, please contact our Technical Services team with a request in writing confirming the specification and build-up of the element in question.
We care about your privacy. That's why we will only use your data to reply to your enquiry. Find out more in our privacy notice. At any moment, you can access, modify or have erased your personal data by sending a request to privacy.insulation@recticel.com.
Please note, after mass updates to retain it's efficiency, our U-value calculator is currently in it's beta stage, please contact our Technical Services team with any specific questions about this or your calculation.
What is a U-value?
A U-value measures how easily heat passes through a building element, such as a wall, roof or floor. It is expressed in watts per square metre Kelvin (W/m²K).
A lower U-value indicates better thermal performance because less heat is transferred through the construction.
The U-value of a building element depends on the complete construction build-up, including the materials used, their thickness and their thermal properties. This means that insulation thickness is only one part of the overall calculation.
Understanding U-values can help building designers and construction professionals compare different construction build-ups and select appropriate insulation solutions for their project.
How do you calculate a U-value?
U-value is calculated from the total thermal resistance of the building element:
U = 1 ÷ total thermal resistance
The calculation takes into account the thermal resistance of the individual layers within the construction build-up, together with relevant surface resistances.
Rather than calculating each layer manually, Recticel Insulation's online U-value calculator allows you to create a construction build-up and assess its indicative thermal performance.
For formal project-specific U-value calculations or technical advice, contact the Recticel Insulation Technical Services team.
U-Value FAQs
Vacuum insulation
Are you planning to insulate a gutter on a terrace, which needs to comply with the required U-value, but you have limited space?
At Recticel Insulation, we are committed to supplying high-quality insulation solutions for flat roofs. This is the reason why we created Deck-VQ - a tailor-made vacuum insulation solution for insulating terraces, where there is limited space.
Deck-VQ ensures that you can achieve the same U-value with your gutter as on your terrace. No more thermal performance losses through the gutter!
To make the installation simple and most efficient, we are happy to provide a customised installation plan.
Contact our Vacuum Insulation specialists to discuss further.
Construction law & regulations
Can I get a U-value calculated for my project using Recticel Insulation products?
Absolutely! Please contact our freephone technical helpline on 0800 085 4079 or use our free of charge U-value calculator here.
What is a good U-value?
A good U-value depends on the type of building element, the construction build-up, the project requirements and applicable Building Regulations.
Generally, a lower U-value indicates better thermal performance, because less heat is transferred through the building element.
The required U-value should be established as part of the overall building design and specification.
Energy efficiency
How do you calculate a U-value?
A U-value is calculated from the total thermal resistance of a building element, taking into account the different materials and layers within the construction build-up.
The basic principle is:
U-value = 1 ÷ total thermal resistance
Recticel Insulation's online U-value calculator can be used to assess the indicative thermal performance of different construction build-ups without having to calculate each layer manually.
What is a U-value?
A U-value measures how easily heat passes through a building element, such as a wall, roof or floor. It is expressed in watts per square metre Kelvin (W/m²K).
The lower the U-value, the better the thermal performance of the building element, as less heat is transferred through it.
What is the difference between a U-value and an R-value?
U-values take into account all elements of a construction, including thermal bridges. They can only be worked out by calculation. The R-value, or thermal resistance, is a measure of the insulation board on its own, dividing the thickness (in metres) by the thermal conductivity (lambda value, W/m.K). The R-value can be used to compare how different thicknesses of products with different lambda values perform comparatively.
Why is U-value important?
U-values are important because they help assess the thermal performance of a building's fabric.
A lower U-value means less heat is transferred through the building element, which can contribute to improved energy efficiency and help projects meet their thermal performance requirements.
Floor
What U-value do I need for a floor?
The required floor U-value depends on the type of floor construction, building design and applicable Building Regulations.
Ground floors, suspended floors and other construction types can have different thermal performance requirements.
Use the U-value calculator to assess different floor construction and insulation build-ups.
Flat roof & terraces
What U-value do I need for a roof?
The required roof U-value depends on the type of roof construction, building design and applicable Building Regulations.
Warm roofs, pitched roofs and other roof constructions can require different insulation solutions and thicknesses.
Recticel's U-value calculator can be used to assess different roof construction build-ups and their indicative thermal performance.
Internal wall
What U-value do I need for a wall?
The required U-value for a wall depends on factors including the building type, construction method, project requirements and applicable Building Regulations.
Different wall constructions can achieve the same target U-value using different materials and insulation thicknesses.
Use the Recticel U-value calculator to assess different wall build-ups and insulation specifications.